More than 30 people from 12 marine stations took part in this event organised by members of the Marseille SOMLIT station (N. Garcia, G. Grégori, M. Lafont, V. Lagadec, S. Nunige, P. Raimbault) from 18 to 20 October 2022 in the OCEANOMED building. The intercomparison consists of a series of exercises carried out annually for all the hydrological variables measured by the SNO SOMLIT requiring a sampling stage (all the parameters in the hydrological and pico-nanoplankton series except temperature and salinity).
The purpose of cross-comparisons is manifold:
Measure the repeatability (between stations) and reproducibility (between stations) of the measurements taken
Refine common protocols on the basis of results, if necessary
Enable operators in the field and analysts from the various SOMLIT teams to meet up in a friendly atmosphere, thereby uniting the teams.
Participate in staff training
The intercomparisons take place as follows: the field operators and analysts from the SOMLIT teams meet at one of the network's marine stations for three days. The day after the equipment is installed, large volumes of water are taken and stored in drums (For Marseille in 2022: 1,000 litres!). The water is transferred to a 350-litre stainless steel sampling tank fitted with 15 Niskin-type taps. The water is taken simultaneously by a member of each team directly from the tank, using the bottle normally used at each station. The usual protocol was then applied to each sample. Dissolved gas parameters (oxygen, pH) are sampled first, followed by nutrients. For particulate parameters, the tank is refilled. Homogenisation is ensured by two paddles located at different levels in the tank. The samples are then taken simultaneously and processed according to the usual protocol, parameter by parameter. Five replicates are carried out for each parameter and per team. Sampling and sample processing (addition of reagents, filtration, etc.) for all the intercomparison parameters are carried out on the same day. Analyses are carried out in the days or weeks that follow, back in the laboratories. The following day is devoted to workshops, generally dedicated to specific work on a particular protocol.
The results are processed statistically in order to identify satisfactory, questionable and doubtful results and any causes of non-conformity. At the end of each intercomparison, a summary document is produced, summarising all the information and results obtained, together with any corrective and/or preventive action taken. A summary of all the intercomparisons is also produced. It highlights the continuous improvement in results since the SOMLIT network quality approach was implemented.